The long range goal of our research is to understand how populations of neurons in early visual cortex represent visual objects, and how that information is used to guide behavior in simple tasks. The specific aims are to assess: 1) how the visual cortex responds to simple contour stimuli and to combinations of two or three contour stimuli, 2) how population activity to contour stimuli change as the animal engages in two types of detection tasks, and 3) how an ideal observer, or the animal, might be able to use the population activity in early visual cortex to perform the detection task. To address these questions we record population activity in primary and secondary visual cortex using optical imaging with voltage sensitive dyes and electrophysiological recordings as animals engage in visual detection tasks. Recording from populations of neurons is necessary to obtain a more complete description of the pattern of activity in visual cortex that results from single contour stimuli or combinations of contour stimuli. Performing these experiments in behaving monkeys is essential if we want to know how the population activity in visual cortex is actually used to guide behavior. Overall, we expect these experiments to provide significant insight into the mechanisms for lateral interactions in visual processing, and into how the pattern of activity across distributed sets of cortical neurons in early visual cortex is related to behavior. Relevance: The purpose of our research is to understand the basic mechanisms by which populations of neurons in the cerebral cortex represent visual objects in the world. Understanding how the cerebral cortex processes information is critical for understanding human behavior, and for understanding how particular diseases or injuries which affect the cerebral cortex, will in turn affect behavior. In the future, a better understanding of cortical processing may allow us to develop better ways to treat brain diseases, or make it possible to develop more effective neuroprosthetic devices. [unreadable] [unreadable] [unreadable]